Zheng Hu

Genome-wide profiling of HPV integration in cervical cancer identifies clustered genomic hot spots and a potential microhomology-mediated integration mechanism

Human papillomavirus (HPV) integration is a key genetic event in cervical carcinogenesis. By conducting whole-genome sequencing and high-throughput viral integration detection, we identified 3,667 HPV integration breakpoints in 26 cervical intraepithelial neoplasias, 104 cervical carcinomas and five cell lines. Beyond recalculating frequencies for the previously reported frequent integration sites POU5F1B (9.7%), FHIT (8.7%), KLF12 (7.8%), KLF5 (6.8%), LRP1B (5.8%) and LEPREL1 (4.9%), we discovered new hot spots HMGA2 (7.8%), DLG2 (4.9%) and SEMA3D (4.9%). Protein expression from FHIT and LRP1B was downregulated when HPV integrated in their introns. Protein expression from MYC and HMGA2 was elevated when HPV integrated into flanking regions. Moreover, microhomologous sequence between the human and HPV genomes was significantly enriched near integration breakpoints, indicating that fusion between viral and human DNA may have occurred by microhomology-mediated DNA repair pathways. Our data provide insights into HPV integration-driven cervical carcinogenesis.

Disruption of HPV16-E7 by CRISPR/Cas System Induces Apoptosis and Growth Inhibition in HPV16 Positive Human Cervical Cancer Cells

High-risk human papillomavirus (HR-HPV) has been recognized as a major causative agent for cervical cancer. Upon HPV infection, early genes E6 and E7 play important roles in maintaining malignant phenotype of cervical cancer cells. By using clustered regularly interspaced short palindromic repeats- (CRISPR-) associated protein system (CRISPR/Cas system), a widely used genome editing tool in many organisms, to target HPV16-E7 DNA in HPV positive cell lines, we showed for the first time that the HPV16-E7 single-guide RNA (sgRNA) guided CRISPR/Cas system could disrupt HPV16-E7 DNA at specific sites, inducing apoptosis and growth inhibition in HPV positive SiHa and Caski cells, but not in HPV negative C33A and HEK293 cells. Moreover, disruption of E7 DNA directly leads to downregulation of E7 protein and upregulation of tumor suppressor protein pRb. Therefore, our results suggest that HPV16-E7 gRNA guided CRISPR/Cas system might be used as a therapeutic strategy for the treatment of cervical cancer.

TALEN-mediated targeting of HPV oncogenes ameliorates HPV-related cervical malignancy

Persistent HPV infection is recognized as the main etiologic factor for cervical cancer. HPV expresses the oncoproteins E6 and E7, both of which play key roles in maintaining viral infection and promoting carcinogenesis. While siRNA-mediated targeting of E6 and E7 transcripts temporarily induces apoptosis in HPV-positive cells, it does not eliminate viral DNA within the host genome, which can harbor escape mutants. Here, we demonstrated that specifically targeting E6 and E7 within host DNA with transcription activator-like effector nucleases (TALENs) induces apoptosis, inhibits growth, and reduces tumorigenicity in HPV-positive cell lines. TALEN treatment efficiently disrupted E6 and E7 oncogenes, leading to the restoration of host tumor suppressors p53 and retinoblastoma 1 (RB1), which are targeted by E6 and E7, respectively. In the K14-HPV16 transgenic mouse model of HPV-driven neoplasms, direct cervical application of HPV16-E7-targeted TALENs effectively mutated the E7 oncogene, reduced viral DNA load, and restored RB1 function and downstream targets transcription factor E2F1 and cycling-dependent kinase 2 (CDK2), thereby reversing the malignant phenotype. Together, the results from our study suggest that TALENs have potential as a therapeutic strategy for HPV infection and related cervical malignancy.

SIX1 Promotes Tumor Lymphangiogenesis by Coordinating TGFβ Signals That Increase Expression of VEGF-C

Lymphatic vessels are one of the major routes for the dissemination of cancer cells. Malignant tumors release growth factors such as VEGF-C to induce lymphangiogenesis, thereby promoting lymph node metastasis. Here, we report that sine oculis homeobox homolog 1 (SIX1), expressed in tumor cells, can promote tumor lymphangiogenesis and lymph node metastasis by coordinating with TGFβ to increase the expression of VEGF-C. Lymphangiogenesis and lymph node metastasis in cervical cancer were closely correlated with higher expression of SIX1 in tumor cells. By enhancing VEGF-C expression in tumor cells, SIX1 could augment the promoting effect of tumor cells on the migration and tube formation of lymphatic endothelial cells (LEC) in vitro and lymphangiogenesis in vivo. SIX1 enhanced TGFβ-induced activation of SMAD2/3 and coordinated with the SMAD pathway to modulate VEGF-C expression. Together, SIX1 and TGFβ induced much higher expression of VEGF-C in tumor cells than each of them alone. Despite its effect in promoting VEGF-C expression, TGFβ could inhibit lymphangiogenesis by directly inhibiting tube formation by LECs. However, the increased production of VEGF-C not only directly promoted migration and tube formation of LECs but also thwarted the inhibitory effect of TGFβ on LECs. That is, tumor cells that expressed high levels of SIX1 could promote lymphangiogenesis and counteract the negative effects of TGFβ on lymphangiogenesis by increasing the expression of VEGF-C. These findings provide new insights into tumor lymphangiogenesis and the various roles of TGFβ signaling in tumor regulation. Our results also suggest that SIX1/TGFβ might be a potential therapeutic target for preventing lymph node metastasis of tumor.

Disruption of human papillomavirus 16 E6 gene by clustered regularly interspaced short palindromic repeat/Cas system in human cervical cancer cells

High-risk human papillomavirus (HPV), especially HPV16, is considered a main causative agent of cervical cancer. Upon HPV infection, the viral oncoprotein E6 disrupts the host tumor-suppressor protein p53, thus promoting malignant transformation of normal cervical cells. Here, we used the newly developed programmable ribonucleic acid-guided clustered regularly interspaced short palindromic repeat (CRISPR)/Cas system to disrupt the HPV16 E6 gene. We showed that HPV16 E6 deoxyribonucleic acid was cleaved at specific sites, leading to apoptosis and growth inhibition of HPV16-positive SiHa and CaSki cells, but not HPV-negative C33A or human embryonic kidney 293 cells. We also observed downregulation of the E6 protein and restoration of the p53 protein. These data proved that the HPV16 E6 ribonucleic acid-guided CRISPR/Cas system might be an effective therapeutic agent in treating HPV infection-related cervical malignancy.

Zinc Finger Nucleases Targeting the Human Papillomavirus E7 Oncogene Induce E7 Disruption and a Transformed Phenotype in HPV16/18-Positive Cervical Cancer Cells

Purpose: Cervical cancer is mainly caused by infections of high-risk human papillomavirus (HR-HPV). Persistent expression of HR-HPV oncogenes E6 and E7 is implicated in malignant transformation. The aim was to provide proof-of-concept data to support use of zinc finger nucleases (ZFN) targeting HPV E7 to treat HPV-related cervical cancer. Experimental Design: We designed and constructed ZFNs that could specifically recognize and cleave HPV16/18 E7 DNA. We tested the cleavage efficiency of selected ZFN16-E7-S2 and ZFN18-E7-S2 by using single-strand annealing (SSA) assay. Cell viability and colony formation assays were used to estimate the inhibition of cell growth that received treatments of ZFNs. Gene disruption of HPV E7 and downstream genes were examined by Western blotting. Cell apoptosis assay was used to test the specificity and efficiency of induction of HPV type-specific apoptosis. We also introduced xenograft formation assays to estimate the potential of inhibition of HPV-related disease. Results: We found ZFN16-E7-S2 and ZFN18-E7-S2 disrupted HPV E7 oncogenes in HPV16/18–positive cervical cancer cells. Both ZFNs effectively led to inhibition of type-specific cervical cancer cell growth, and specifically induced apoptosis of corresponding HPV16- and HPV18-positive cervical cancer cell lines. ZFN16-E7-S2 and ZFN18-E7-S2 also repressed xenograft formation in vivo. Conclusion: ZFNs targeting HPV16/18 E7 could effectively induce disruption of E7 oncogenes and lead to type-specific and efficient growth inhibition and apoptosis of HPV-positive cells. ZFNs targeting HPV16/18 E7 oncogenes could be used as novel therapeutic agents for the treatment of HPV-related cervical cancer. Clin Cancer Res; 20(24); 6495–503. ©2014 AACR.

Amplification and overexpression of TP63 and MYC as biomarkers for transition of cervical intraepithelial neoplasia to cervical cancer.

Objective Biopsy confirmed that cervical intraepithelial neoplasia (CIN) may naturally regress or progress. Currently, the risk assessment for CIN progression to cervical cancer is still not satisfactory in clinical practice. We investigated copy number and protein expression of TP63 and MYC and explored the possibility to use them as progression biomarkers. Methods Copy numbers of TP63 and MYC, as well as human papilloma virus (HPV) integration status, were determined by fluorescence in situ hybridization in 39 patients with CIN and 66 patients with cervical cancer. Corresponding protein expressions were analyzed by immunohistochemistry. Receiver operating characteristic curves were used to measure the diagnostic test performance for the detection of cervical cancer from CIN. Sensitivity and specificity values of biomarkers were calculated. Results The average copy number and expression of TP63 and MYC, as well as the HPV integration rate, increased in the progression of CIN to cervical cancer. Receiver operating characteristic analysis for detection of cervical cancer resulted in area under the curve (AUC) values of TP63 copy number (AUC, 0.96; 95% confidence interval [CI], 0.91–1.00), MYC copy number (AUC, 0.92; 95% CI, 0.85–0.96), TP63 expression (AUC, 0.73; 95% CI, 0.61–0.85), and HPV-16 integration (AUC, 0.73; 95% CI, 0.60–0.85). MYC expression was not able to statistically distinguish cancer from CIN (P = 0.393). The combinations increased the specificity slightly but not sensitivity. Among them, TP63 amplification showed the best diagnostic performance. Conclusions Amplification and overexpression of TP63 and MYC, and HPV integration rate, are associated with the transition of CIN to cervical cancer. Future studies on these biomarkers will help to assess the risk of CIN progression.ObjectiveBiopsy confirmed that cervical intraepithelial neoplasia (CIN) may naturally regress or progress. Currently, the risk assessment for CIN progression to cervical cancer is still not satisfactory in clinical practice. We investigated copy number and protein expression of TP63 and MYC and explored the possibility to use them as progression biomarkers. MethodsCopy numbers of TP63 and MYC, as well as human papilloma virus (HPV) integration status, were determined by fluorescence in situ hybridization in 39 patients with CIN and 66 patients with cervical cancer. Corresponding protein expressions were analyzed by immunohistochemistry. Receiver operating characteristic curves were used to measure the diagnostic test performance for the detection of cervical cancer from CIN. Sensitivity and specificity values of biomarkers were calculated. ResultsThe average copy number and expression of TP63 and MYC, as well as the HPV integration rate, increased in the progression of CIN to cervical cancer. Receiver operating characteristic analysis for detection of cervical cancer resulted in area under the curve (AUC) values of TP63 copy number (AUC, 0.96; 95% confidence interval [CI], 0.91–1.00), MYC copy number (AUC, 0.92; 95% CI, 0.85–0.96), TP63 expression (AUC, 0.73; 95% CI, 0.61–0.85), and HPV-16 integration (AUC, 0.73; 95% CI, 0.60–0.85). MYC expression was not able to statistically distinguish cancer from CIN (P = 0.393). The combinations increased the specificity slightly but not sensitivity. Among them, TP63 amplification showed the best diagnostic performance. ConclusionsAmplification and overexpression of TP63 and MYC, and HPV integration rate, are associated with the transition of CIN to cervical cancer. Future studies on these biomarkers will help to assess the risk of CIN progression.

Proteomics-based identification of VDAC1 as a tumor promoter in cervical carcinoma

We used oxidative isotope-coded affinity tags (OxICAT) to investigate the global redox status of proteins in human papillomavirus (HPV)-related cervical cancer cells, in order to identify a potential target for gene therapy. Voltage-dependent anion channel 1 (VDAC1) was found to be highly oxidized in HPV-positive cervical cancer cells. VDAC1 expression correlated significantly with the invasion of cervical cancer, the grade of cervical intraepithelial neoplasia (CIN) and the expression of HPV16 E7 in CIN. Knockdown of VDAC1 in cell lines increased the rate of apoptosis, while overexpression of the VDAC1 (respectively) partly reversed the effect. Thus, VDAC1 may promote the malignant progression of HPV-related disease, and treatments designed to suppress VDAC1 could prevent the progression of HPV-induced cervical disease.

TALENs-mediated gene disruption of FLT3 in leukemia cells: Using genome-editing approach for exploring the molecular basis of gene abnormality.

Novel analytic tools are needed to elucidate the molecular basis of leukemia-relevant gene mutations in the post-genome era. We generated isogenic leukemia cell clones in which the FLT3 gene was disrupted in a single allele using TALENs. Isogenic clones with mono-allelic disrupted FLT3 were compared to an isogenic wild-type control clone and parental leukemia cells for transcriptional expression, downstream FLT3 signaling and proliferation capacity. The global gene expression profiles of mutant K562 clones and corresponding wild-type controls were compared using RNA-seq. The transcriptional levels and the ligand-dependent autophosphorylation of FLT3 were decreased in the mutant clones. TALENs-mediated FLT3 haplo-insufficiency impaired cell proliferation and colony formation in vitro. These inhibitory effects were maintained in vivo, improving the survival of NOD/SCID mice transplanted with mutant K562 clones. Cluster analysis revealed that the gene expression pattern of isogenic clones was determined by the FLT3 mutant status rather than the deviation among individual isogenic clones. Differentially expressed genes between the mutant and wild-type clones revealed an activation of nonsense-mediated decay pathway in mutant K562 clones as well as an inhibited FLT3 signaling. Our data support that this genome-editing approach is a robust and generally applicable platform to explore the molecular bases of gene mutations.

CLDN1 expression in cervical cancer cells is related to tumor invasion and metastasis

Even though infection with human papillomaviruses (HPV) is very important, it is not the sole cause of cervical cancer. Because it is known that genetic variations that result from HPV infection are probably the most important causes of cervical cancer, we used human whole genome array comparative genomic hybridization to detect the copy number variations of genes in cervical squamous cell carcinoma. The results of the array were validated by PCR, FISH and immunohistochemistry. We find that the copy number and protein expression of claudin-1 (CLDN1) increase with the progression of cervical cancer. The strong positive staining of CLDN1 in the cervical lymph node metastasis group received a significantly higher score than the staining in the group with no lymph node metastasis of cervical cancer tissues. The overexpression of CLDN1 in SiHa cells can increase anti-apoptosis ability and promote invasive ability of these cells accompanied by a decrease in expression of the epithelial marker E-cadherin as well as an increase in the expression of the mesenchymal marker vimentin. CLDN1 induces the epithelial-mesenchymal transition (EMT) through its interaction with SNAI1. Furthermore, we demonstrate that CLDN1 overexpression has significant effects on the growth and metastasis of xenografted tumors in athymic mice. These data suggest that CLDN1 promotes invasion and metastasis in cervical cancer cells via the expression of EMT/invasion-related genes. Therefore, CLDN1 could be a potential therapeutic target for the treatment of cervical cancer.